1. Technical Field
The present invention generally relates to wireless communication between devices. In particular, the present invention relates to techniques for reducing latency and improving beacon reception in devices, such as wireless local area network (WLAN) devices, that are capable of providing multiple wireless interfaces via a single radio.
2. Background Art
Wireless communication is increasingly becoming the dominant method of interconnecting devices at home, in work environments, and elsewhere. In accordance with a traditional Wi-Fi (i.e., 802.11b/g/n/e/ac standard) WLAN architecture, at least one access point (AP) acts as a central hub that connects Internet service providers and local devices such as laptop computers, tablets, phones, printers, music devices, and televisions. In a traditional WLAN architecture, each local device wirelessly communicates with only one AP at a given time, and each AP may wirelessly communicate with several local devices in turn.
As the popularity of including Wi-Fi interfaces in consumer electronic devices has increased, newer WLAN architectures have emerged that enable local devices to stream media directly to other local devices in a peer-to-peer (P2P) fashion. Communicating in a P2P manner can enable, for example, a consumer to stream audio content being downloaded from an Internet music service onto his handheld device (e.g., a mobile phone or tablet) to a speaker in his home. As another example, communicating in a P2P manner can enable a consumer to stream a movie being downloaded from an Internet movie service onto his handheld device to a television in his home. Examples of P2P Wi-Fi communication are described in the Wi-Fi Direct P2P and Miracast protocol standards.
A P2P WLAN may include an AP, a device having multiple wireless interfaces (a “multi-interface device”), and a P2P device. The multi-interface device concurrently communicates with the AP via a first wireless interface and with the P2P device via a second wireless interface. In accordance with the example use cases discussed above, the multi-interface device may comprise a handheld device such as a mobile phone or tablet and the P2P device may comprise a speaker or television, although these examples are not intended to be limiting. Because many wireless devices, especially handheld devices, are power constrained, it is often impractical for them to include more than one radio to communicate with other wireless devices. To address this issue, some multi-interface devices utilize software intelligence to implement two wireless interfaces simultaneously using a single radio. This mode of operation is sometimes referred to as a concurrent mode of operation. In this mode of operation, the two wireless interfaces can operate on the same channel or a different channel. If the interfaces are operating on the same channel, this may be referred to as concurrent same channel operation. If the interfaces are operating on different channels, this may be referred to as VSDB (Virtual Simultaneous Dual Band) or VSDC (Virtual Simultaneous Dual Channel) operation.
In accordance with VSDB or VSDC operation, software intelligence in the multi-interface device utilizes time division multiplexing (TDM) to periodically switch between the two wireless interfaces so as to effectively receive beacon frames (or simply “beacons”) that are periodically sent from two different wireless devices (e.g., an AP and a P2P device). However, there is an overhead associated with switching between channels/bands in this manner. This overhead includes, for example, the time associated with resetting the radio for a particular wireless interface. Consequently, if the beacons being transmitted by the two different wireless devices are too close together in time, it becomes practically impossible to switch from one wireless interface to the other in time quickly enough to avoid missing beacons.
Some software mechanisms exist that address this problem by alternating between the two wireless interfaces such that during a first time period, beacons will be received by the first wireless interface while beacons are missed by the second wireless interface, and then during a second time period, beacons will be received by the second wireless interface while beacons are missed by the first wireless interface. However, this approach introduces latencies which are unacceptable for applications such as screen sharing and Wi-Fi display.